My understanding of the situation is that blocking access to a driveway regardless whether it's public or private is against the regulations:
Have a look at the interpretation section of the 1993 Reg and apply them to section 36 of the 1997 Regs:
http://www.irishstatutebook.ie/1997/en/si/0182.html#zzsi182y1997a36
As regards Drink Driving/tax /ins the legislation defines what a public place is. Going by this definition a private carpark (eg pub carpark) /private grounds of a school/church etc would be an offence to drive drunk, no ins etc.
A situation where it would not be an offence to drive drunk, no ins would be on ones own land such as a farm or whatever. Essentially the public do not 'habitually cross' this property.